[HTTPS-Everywhere] Updated 'Creating Rulesets' page

[Jacob Hoffman-Andrews]

Hi all,

I just put up a pull request for an updated version of the 'Creating
Rulesets' page:
https://github.com/EFForg/https-everywhere/pull/1298

You can read just the doc here:

https://github.com/EFForg/https-everywhere/blob/doc/docs/rulesets.html

I'd like to get some eyes on this before I put it on the EFF website, so
please take a look and let me know of any issues. You can comment on the
PR, make pull requests against the 'doc' branch, or reply here.

Thanks,
Jacob